What I'd definitely do is install a filter (of sorts) on your CDN that serves a reduced-size, watermarked version of your images, for the unavoidable hotlinking.
As for policing user-generated content sites... it kinda depends. If used on a forum, for example for educational purposes (explaining something), I wouldn't bother. Fair use, live and let live, etc - they're getting a watermarked version (link to the source, copyright etc) anyway.
For commercial use, do keep policing them. There should be software and websites out there (google image search by image, for example) to make it easier for you.
Thanks. Some times those images are cropped to remove our watermark (we don't want to make it too strong, after all, it's very important that you can see the anatomy structure as clearly as possible on our website. precision and detail is key)
We're doing some searches, but it takes time. Of course small forums for fair use is fine, but we've seen our illustrations on sites that allow users to build online quizzes and flashcards, which kinda competes with our own product. If we have to keep searching for our own images on those sites, this can be very costly for us in the long run. We hope the site owners will take responsibility for this. In any case, we haven't contacted them yet, so we'll have to wait and see. We hope they understand our situation and will do whatever they can to help.
Was just curious about the legal (or even ethical) situation in these cases of repeat offenders which are user-generated...
I think what Cthulu_ says is to serve clean and nice pictures to people coming through your server, and instead serve heavy watermarked versions for hotlinked links.
I'm not sure how this can be arranged with a CDN, but it's probably relatively easy/there's a painless way
yes, I understand. But even if technically possible, it won't really solve our problem. It might solve hotlinking, but not copy&pasting our images / cropping them and uploading them elsewhere, which happens probably just as frequently if not more frequently than just using our own CDN link.
Furthermore, there's a small hidden benefit of people who do hotlink to our CDN - it makes it potentially easier to trace.
Copy&pasters would require a more sophisticated search which is either labour intensive to do manually for us, or costs money to do via API.
My main concern is not about technical aspects, but rather legal, ethical and practical. Primarily, how to deal with sites that rely on user-generated (or user-stolen) content where offenders might keep on doing this...
Register a LLC in the US, which is not expensive at all, this should get you on the road to sending DMCA takedowns to at least the US sites hosting your content. Here on HN, search for the user named grellas, who is a lawyer and may be able to guide you in that regard.
Disclaimer: IANAL
Nice site! Like the illustrations, had fun brushing up on things from my medical school days.
As for policing user-generated content sites... it kinda depends. If used on a forum, for example for educational purposes (explaining something), I wouldn't bother. Fair use, live and let live, etc - they're getting a watermarked version (link to the source, copyright etc) anyway.
For commercial use, do keep policing them. There should be software and websites out there (google image search by image, for example) to make it easier for you.
disclaimer: IANAL etc.